This invention relates to an actuator arrangement and in particular to an actuator arrangement suitable for use in driving the leading edge slats or other control surfaces of an aircraft wing for movement between a fully retracted or stowed position and a fully extended or deployed position.
One common actuator arrangement for use in such applications includes a toothed rack or track, the teeth of which mesh with the teeth of a rotatable, motor driven pinion mounted upon a drive shaft. The drive shaft and pinion gear are mounted for rotation on the aircraft wing, and the track is secured to the leading edge slat. It will be appreciated that rotation of the pinion gear drives the track, and associated slat, for movement relative to the wing, thus permitting the slat to be moved between stowed and deployed positions. The track is typically of part circular, curved form, creating a virtual hinge line below the level of the wing, and is supported in such a manner as to guide the slat so that the slat follows a curved path of movement around the virtual hinge line when travelling between its stowed and deployed positions.
It will be appreciated that, when stowed, the track extends a considerable distance into the wing and, typically, in order to accommodate the track, openings are formed through a front spar of the wing to allow the track to extend into the wing. Often, the track is accommodated in a section of the wing that contains a fuel tank, and so relatively complex sealing arrangements have to be provided in order to prevent the escape of fuel. For example, a track can may be provided immediately behind the front spar, within the fuel tank, into which at least part of the track can be moved. In such an arrangement, the track can is sealed to the front spar/fuel tank to prevent leakage of fuel from the fuel tank at this point. The cost, complexity and quality issues associated with such an arrangement are undesirable.
Increasingly, composite materials are being used in the construction of aircraft wings. Where the front spar of the aircraft wing is manufactured from a composite material, the formation of openings therein, for example to allow the movement of the track of a slat, is undesirable as the provision of such openings significantly weakens the front spar. The need to accommodate the provision of openings therein whilst maintaining sufficient strength places severe restrictions on the design of front spar.